A hand exoskeleton is designed and constructed to achieve five hand positions: (1) fully extended, (2) hook fist, (3) right angle to the palm, (4) straight fist,and (5) fully flexed. These hand orientations comprise the five positions defining a rehabilitation exercise known as tendon glide. The device is significant in its ability to move the two joints distal to the palm independently of the joint adjoining the palm, without requiring bulky, rigid hardware located on the finger. Movement of the finger is achieved through hydraulically activated fluidic artificial muscles (FAMs). FAMs are soft, biomimetic actuators consisting of an expandable bladder encased in a braided sheath. FAMs show improved force-to-weight ratios, cost, and alignment strategies over traditional, rigid hydraulic cylinders and allow forces to be applied across a flexed joint of the finger as it straightens. A direct model of the relationship between the volume transferred to the FAM by the hydraulic cylinder and the strain of the FAM is developed and validated through experiment. The strain volume relationship remains constant regardless of load, enabling streamlined models and control algorithms. Position-based control of the FAMs is achieved, in both simulation and experiment, with a Proportional Integral (PI) controller and a Model Reference Adaptive Controller (MRAC). The PI controller is a linear algorithm characterized by constant controller gains. Alternatively, MRAC is an adaptive control algorithm characterized by time varying controller gains, which can guarantee convergence of the actual system to a defined reference system. The resultant device is a wearable exoskeleton actuated by FAMs and governed by novel control architecture. The exoskeleton is capable of guiding a finger through all five positions of tendon glide.
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